Biologically, cholesterol is eliminated from the body by conversion into bile acids and excretion as neutral steroids. Bile acids are synthesized from cholesterol in the liver and enter the bile as glycine and taurine conjugates. They are released in salt form in bile during digestion and act as detergents to solubilize and consequently aid in the digestion of dietary fats. Following digestion, bile acid salts are mostly reabsorbed by active transport in the ileum, complexed with proteins, and returned to the liver through hepatic portal veins. The small amount of bile acid salts not reabsorbed in the ileum is excreted via the distal ileum and large intestine, as a portion of the fecal material.
Therefore, reabsorption of bile acids, which can be present as the corresponding salts or conjugates, from the intestine conserves lipoprotein cholesterol in the bloodstream. As such, reducing reabsorption of bile acids within the intestinal tract can lower levels of bile acids circulating in the enterohepatic system thereby promoting replacement of bile acids through de novo synthesis from cholesterol, in the liver. The result is a lowering of circulating blood cholesterol levels.
One method of reducing the quantity of bile acids that are reabsorbed is the oral administration of compounds that sequester the bile acids within the intestinal tract and cannot themselves be absorbed. The sequestered bile acids consequently are excreted.
A need exists for sequestrants that bind bile acid salts and conjugates.
The present invention relates to a method for sequestering bile acids in a patient and to particular polymers for use in the method. The method comprises the step of administering to the patient a therapeutically effective amount of a polymer characterized by a polyether backbone and amino or ammonium groups pendant therefrom. The amino nitrogen atoms can be substituted by one or more substituents independently selected from among substituted and unsubstituted, normal, branched and cyclic alkyl groups, and aryl groups. When the polymer comprises pendant ammonium or quaternary ammonium groups, the polymer will be associated with a suitable anion, such as a conjugate base of a pharmaceutically acceptable acid.
The polymer to be administered can be a homopolymer or a copolymer. When the polymer is a copolymer, the polymer can comprise at least two distinct side chains.
The polymer can be linear, branched or crosslinked. In one embodiment, the polymer is crosslinked via the incorporation of a multifunctional comonomer. In another embodiment, the polymer is crosslinked via bridging groups which link amino nitrogen atoms on different polymer strands.
The invention further relates to a method for reducing blood cholesterol, treating atherosclerosis, treating hypercholesterolemia and/or reducing plasma lipid content of a mammal.
The features and other details of the invention will now be more particularly described and pointed out in the claims. It will be understood that the particular embodiments of the invention are shown by way of illustration and not as limitations of the invention. The principal features of the invention can be employed in various embodiments without departing from the scope of the present invention.
In one aspect, the present invention relates to a method for sequestering bile acids in a patient and to particular polymers for use in the methods. The method comprises the step of orally administering to a mammal, such as a human, a therapeutically effective amount of a new class of polyether-based polymers comprising a polyether backbone having at least one amino or ammonium group pendant therefrom.
The invention also provides a method for reducing blood cholesterol, treating atherosclerosis, treating hypercholesterolemia and/or reducing plasma lipid content of a mammal. The methods comprises the step of orally administering to a mammal, such as a human, a therapeutically effective amount of a new class of polyether-based polymers comprising a polyether backbone having at least one amino or ammonium group pendant therefrom.
As used herein, the term xe2x80x9ctherapeutically effective amountxe2x80x9d refers to an amount which is sufficient to bind bile acids, reduce blood cholesterol, treat atherosclerosis and/or treat hypercholesterolemia in a patient. The patient can be an animal, for example, a mammal such as a human.
In one embodiment, the polymer to be administered is characterized by a repeat unit of Formula I, 
wherein n and m are each, independently, 0, 1 or 2 and p is 0 to about 6. R1, R2 and R3 are each, independently, a hydrogen atom; a substituted or unsubstituted, linear, branched or cyclic alkyl group; or a substituted or unsubstituted aryl group. Suitable alkyl and aryl substituents include aryl groups; halogen atoms, such as fluorine, chlorine, bromine and iodine atoms; alkyl groups; hydroxy; primary, secondary and tertiary amino; quaternary ammonium; alkoxy; carboxamido; sulfonamido; aryl; hydrazido; guanidyl; and ureyl. Xxe2x88x92 is a pharmaceutically acceptable anion. Examples of suitable anions include chloride, bromide, citrate, tartrate, lactate, methanesulfonate, acetate, formate, maleate, fumarate, malate, succinate, malonate, sulfate, hydrosulfate, L-glutamate, L-aspartate, pyruvate, mucate, benzoate, glucuronate, oxalate, ascorbate, acetylglycinate, the conjugate base of a fatty acid (e.g., oleate, laurate, myristate, stearate, arachidate, behenate, arachidonate) and combinations thereof. In a preferred embodiment, Xxe2x88x92 is chloride.
In one embodiment, at least one of R1, R2 and R3 is a hydrophobic group, preferably a hydrophobic alkyl group. xe2x80x9cHydrophobic groupxe2x80x9d, as the term is used herein, is a chemical group which, as a separate entity, is more soluble in octanol than water. For example, the octyl group (C8H17) is hydrophobic because its parent alkane, octane, has greater solubility in octanol than in water. The hydrophobic group can be a saturated or unsaturated, substituted or unsubstituted hydrocarbon group. Such groups include substituted and unsubstituted, normal, branched or cyclic alkyl groups having at least about four, preferably at least about six, carbon atoms, substituted or unsubstituted arylalkyl or heteroarylalkyl groups and substituted or unsubstituted aryl or heteroaryl groups. Preferably the hydrophobic group includes an alkyl group of between about four and thirty carbon atoms. More preferably the hydrophobic group includes an alkyl group of between six and about fourteen carbon atoms. Suitable hydrophobic groups include, for example, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-eicosyl. Other examples of hydrophobic groups include haloalkyl groups of at least about four, preferably about six, carbon atoms (e.g., 10-halodecyl), hydroxyalkyl groups of at least about four, preferably about six, carbon atoms (e.g., 11-hydroxyundecyl), and aralkyl groups (e.g., benzyl).
The polymer to be administered can also be characterized by a repeat unit of Formula I in which one of the substituents R1, R2 and R3 is absent. For example, when at least one of R1, R2 and R3 is a hydrogen atom, the repeat unit can also exist in the deprotonated basic form.
In one embodiment, the polymer to be administered is characterized by a repeat unit of Formula I wherein n is 1, m is 0 and p is 1. In this embodiment, the polymer can be, for example, an amino- or ammonium-substituted poly(epichlorohydrin) polymer.
The polymer to be administered can be a homopolymer or a copolymer. In one embodiment, the polymer is a copolymer characterized by two different repeat units of Formula I in which at least one of R1, R2 and R3 in the first repeat unit of Formula I differs from R1, R2 or R3 in the second repeat unit of Formula I. In another embodiment, the polymer is a copolymer characterized by a first repeat unit of Formula I and a second repeat unit of Formula II, 
where n and m are each, independently, 0, 1 or 2 and Y is a hydrogen atom, an alkyl group or a chloromethyl group. In a preferred embodiment, n is 1 and m is 0.
In one embodiment, the polymer to be administered is characterized by a repeat unit of Formula I wherein at least one of R1, R2 and R3 is an ammonioalkyl group.
Suitable ammonioalkyl group are of the general formula: 
wherein R4, R5 and R6 are each, independently, a hydrogen atom or a C1-C30 alkyl group; n is an integer from 2 to about 20, preferably from 3 to about 6; and Xxe2x88x92 is a pharmaceutically acceptable anion as discussed above. In one embodiment, at least one of R4, R5 and R6 is a hydrophobic alkyl group having from 4 to about thirty carbon atoms. In another embodiment, the alkylene group, xe2x80x94(CH2)nxe2x80x94 can be substituted with a suitable substituent as described above. Suitable examples of ammonioalkyl groups include, but are not limited to,
4-(dioctylmethylammonio)butyl;
3-(dodecyldimethylammonio)propyl;
3-(octyldimethylammonio)propyl;
3-(decyldimethylammonio)propyl;
5-(dodecyldimethylammonio)pentyl;
3-(cyclohexyldimethylammonio)propyl;
3-(decyldimethylammonio)-2-hydroxypropyl;
3-(tridecylammonio)propyl;
3-(docosyldimethylammonio)propyl;
4-(dodecyldimethylammonio)butyl;
3-(octadecyldimethylammonio)propyl;
3-(hexyldimethylammonio)propyl;
3-(methyldioctylammonio)propyl;
3-(didecylmethylammonio)propyl;
3-(heptyldimethylammonio)propyl;
3-(dimethylnonylammonio)propyl;
6-(dimethylundecylammonio)hexyl;
4-(heptyldimethylammonio)butyl;
3-(dimethylundecylammonio)propyl; and
3-(tetradecyldimethylammonio)propyl.
The polymer can be linear or cross-linked. For example, the polymer can be cross-linked by incorporation in the polymer of a multifunctional co-monomer, for example, a co-monomer comprising two or more epoxy groups. Suitable multifunctionl co-monomers include butanedioldiglycidyl ether, ethanedioldiglycidyl ether, diglycidyl 1,2-cyclohexanedicarboxylate, N,N-diglycidyl-4-glycidyloxyaniline, 1,2,7,8-diepoxyoctane, and 1,2,3,4-diepoxybutane.
The polymer can also be crosslinked by a bridging unit which links amino groups on adjacent polymer strands. For example, the polymer can comprise a repeat unit of Formula I wherein R1, R2 or R3 is a bridging unit which connects the nitrogen atom of Formula I with a nitrogen atom on a different polymer strand. Suitable bridging units include straight chain or branched, substituted or unsubstituted alkylene groups, alkylene bis(cycloalkyl) groups, bis(alkyl)amine and tris(alkyl)amine groups, diacylalkylene groups, diacylarene groups and alkylene bis(carbamoyl) groups. Suitable bridging units include, for example, xe2x80x94(CH2)nxe2x80x94, wherein n is an integer from about 2 to about 20; xe2x80x94CH2xe2x80x94CH(OH)xe2x80x94CH2xe2x80x94; xe2x80x94C(O)CH2CH2C(O)xe2x80x94; xe2x80x94CH2xe2x80x94CH(OH)xe2x80x94Oxe2x80x94(CH2)mxe2x80x94Oxe2x80x94CH(OH)xe2x80x94CH2xe2x80x94, xe2x80x94(C6H10)xe2x80x94(CH2)mxe2x80x94(C6H10)xe2x80x94 and N[(CH2)m]3xe2x80x94, where m is an integer from about 1 to about 4; xe2x80x94C(O)xe2x80x94(C6H2(COOH)2)xe2x80x94C(O)xe2x80x94 and xe2x80x94C(O)NH(CH2)pNHC(O)xe2x80x94, where p is an integer from about 2 to about 20; and xe2x80x94(OCH2CH2)xxe2x80x94, where x is an integer from 1 to about 100. In another embodiment, the polymer can comprise a repeat unit of Formula I wherein R1, R2 or R3 is a covalent bond which connects the nitrogen atom of Formula I with a nitrogen atom on a different polymer strand.
Polymers of use in the present method can be prepared using techniques known in the art of polymer synthesis. In a preferred embodiment, the polymer backbone is formed by polymerization of epichlorohydrin. The resulting poly(epichlorohydrin) is characterized by repeat units of Formula II where m is 1, n is 0 and Y is a chloromethyl group. This repeat unit can be then be functionalized, for example, by reaction with ammonia or a primary, secondary or tertiary amine, to form a repeat of Formula I.
A crosslinked polymer can be prepared by co-polymerizing epichlorohydrin and a multifunctional co-monomer. Suitable multifunctional monomers include compounds having 2 or more epoxy groups. Examples of such multifunctional monomers include butanedioldiglycidyl ether, ethanedioldiglycidyl ether, diglycidyl 1,2-cyclohexane-dicarboxylate, N,N-diglycidyl-4-glycidyloxyaniline, 1,2,7,8-diepoxyoctane, and 1,2,3,4-diepoxybutane.
A crosslinked polymer which is characterized by a repeat unit of Formula I in which R1 is absent can be crosslinked by reacting the polymer with one or more crosslinking agents having two or more functional groups, such as electrophilic groups, which react with amine groups to form a covalent bond. Crosslinking in this case can occur, for example, via nucleophilic attack of the polymer amino groups on the electrophilic groups. This results in the formation of a bridging unit which links two or more amino nitrogen atoms from different polymer strands. Suitable crosslinking agents of this type include compounds having two or more groups selected from among acyl chloride, epoxide, and alkyl-X, wherein X is a suitable leaving group, such as a halo, tosyl or mesyl group. Examples of such compounds include epichlorohydrin, succinyl dichloride, butanedioldiglycidyl ether, ethanedioldiglycidyl ether, pyromellitic dianhydride and dihaloalkanes. The crosslinking agent can also be an xcex1,xcfx89-alkylene diisocyanate, for example OCN(CH2)pNCO, wherein p is an integer from about 2 to about 20. The polymer can be reacted with an amount of crosslinking agent equal to from about 0.5 to 20 mole percent relative to the amino groups within the polymer, depending upon the extent of crosslinking desired.
In another embodiment, crosslinked polymers comprising a repeat unit of Formula I wherein one of R1, R2 and R3 is a bridging group can be prepared by reacting a polymer comprising a repeat unit of Formula II wherein Y is a chloromethyl group with a crosslinking agent which comprises a bridging group which is bonded to two or more terminal amino groups (e.g., xcex1,xcfx89-diaminoalkanes). For example, a polymer comprising a repeat unit of Formula II wherein Y is a chloromethyl group can be reacted with 1,12-diaminododecane to produce a crosslinked polymer comprising a repeat unit of Formula I, wherein one of R1, R2 and R3 is a dodecyl bridging group which links two repeat units of Formula I on adjacent polymer strands. Suitable multifunctional crosslinking agents of this type can be linear, branched, cyclic, substituted, unsubstitued, saturated or contain one or more units of unsaturation and include, 1,4-diaminobutane, 1,6-diaminohexane, 1,10-diaminodecane, 1,12-diaminododecane, N,Nxe2x80x2-dimethyl-1,6-hexanediamine, N,Nxe2x80x2-dibutyl-1,6-hexanediamine, N,Nxe2x80x2-bis(3-aminopropyl)ethylenediamine, 4,4xe2x80x2-methylene bis(cyclohexylamine), hydrazine, tris(2-aminoethyl)amine and the like. The polymer of this embodiment can be crosslinked to the desired degree by altering the quantity of crosslinking agent that is reacted with the polymer comprising a repeat unit of Formula II.
In another aspect, the invention provides novel polymers having a polyether backbone and at least one amino or ammonium group pendant therefrom as described herein.
The present invention further relates to polymers having a polyether backbone and at least one amino or ammonium group pendant therefrom, as described herein, for use in therapy (including prophylaxis) or diagnosis, and to the use of such a polymer for the manufacture of a medicament for the treatment of a particular disease or condition as described herein (e.g., atherosclerosis, hypercholesterolemia).
Polymers of use in the present method are, preferably, of a molecular weight which enables them to reach and remain in the gastrointestinal tract for a sufficient period of time to sequester a significant amount of bile acid. The polymers are, thus, of sufficient size or are sufficiently crosslinked so as to minimize or prevent their absorption from the mammalian gastrointestinal tract. Suitable linear or branched (non-crosslinked) polymers of the invention are of a molecular weight greater than about 2,000 Daltons. Crosslinked polymers, however are not generally characterized by molecular weight. The crosslinked polymers discussed herein are, preferably, sufficiently crosslinked to resist absorption from the mammalian gastrointestinal tract.
The polymers of the invention are non-toxic and stable when ingested by a mammal. By xe2x80x9cnon-toxicxe2x80x9d it is meant that when ingested in therapeutically effective amounts neither the polymers themselves nor any ions released into the body upon ion exchange are harmful. By xe2x80x9cstablexe2x80x9d it is meant that when ingested in therapeutically effective amounts the polymers do not decompose, in vivo, to form potentially harmful by-products, and remain substantially intact so that they can transport material out of the body.
The polymer can be administered orally to a patient in a dosage of about 1 mg/kg/day to about 1 g/kg/day, preferably between about 1 mg/kg/day to about 200 mg/kg/day. The particular dosage can depend on the individual patient (e.g., the patient""s weight, age and the extent of bile acid sequestration required). The polymer can be administered either in hydrated or dehydrated form, and can be flavored or added to a food or drink, if desired, to enhance patient acceptance. Additional inert ingredients, such as artificial coloring agents, may be added as well.
Examples of suitable forms for administration include pills, tablets, capsules, and powders (i.e. for sprinkling on food). The pill, tablet, capsule or powder can be coated with a substance capable of protecting the composition from the gastric acid in the patient""s stomach for a period of time sufficient for the composition to pass undisintegrated into the patient""s small intestine. The polymer can be administered alone, admixed with a carrier, diluted by a carrier, or enclosed within a carrier which may be in the form of a capsule, sachet, paper or other container. When the carrier serves as a diluent, it may be a solid, semi-solid or liquid material which acts as a vehicle, excipient or medium for the polymer. Thus, the compositions can be in the form of tablets, pills, powders, lozenges, sachets, cachets, elixirs, suspensions, syrups, aerosols, (as a solid or in a liquid medium), soft or hard gelatin capsules, sterile packaged powders, and the like. Examples of suitable carriers, excipients, and diluents include foods, drinks, lactose, dextrose, sucrose, sorbitol, mannitol, starches, gum acacia, alginates, tragacanth, gelatin, calcium silicate, microcrystalline cellulose, polyvinylpyrrolidone, cellulose, methyl cellulose, methylhydroxybenzoates, propylhydroxybenzoates and talc.
The methods described herein can comprise the administration of a polyether-based polymer of the invention in combination with any known or later developed antihyperlipoproteinemic or cholesterol lowering agent or agents, for example, aryloxyalkanoic acid derivatives, HMG CoA reductase inhibitors, nicotinic acid derivatives, thyroid hormones and analogs and other bile acid sequestrants to bind bile acids, reduce blood cholesterol, treat atherosclerosis and/or treat hypercholesterolemia.